Neutrinoless Double Beta Decay in LRSM with Natural Type-II seesaw Dominance

TL;DR

This paper investigates neutrinoless double beta decay in left-right symmetric models with natural type-II seesaw dominance, highlighting new contributions from heavy neutrinos and right-handed currents, constraining neutrino masses and hierarchy.

Contribution

It introduces a model where all physical masses and mixings are expressed in terms of neutrino oscillation parameters, enabling direct constraints on neutrino masses from decay data.

Findings

New contributions to 0νββ decay from heavy neutrinos and right-handed currents.

Current experimental bounds constrain the lightest neutrino mass and favor normal hierarchy.

The model allows large Dirac neutrino masses consistent with observed neutrino oscillations.

Abstract

We present a detailed discussion on neutrinoless double beta decay within a class of left-right symmetric models where neutrino mass originates by natural type-II seesaw dominance. The spontaneous symmetry breaking is implemented with doublets, triplets and bidoublet scalars. The fermion sector is extended with an extra sterile neutrino per generation that helps in implementing the seesaw mechanism. The presence of extra particles in the model exactly cancels type-I seesaw and allows large value for Dirac neutrino mass matrix $M_D$. The key feature of this work is that all the physical masses and mixing are expressed in terms of neutrino oscillation parameters and lightest neutrino mass thereby facilitating to constrain light neutrino masses from $0\nu\beta\beta$ decay. With this large value of $M_D$ new contributions arise due to; i) purely left-handed current via exchange of heavy right-handed neutrinos as well as sterile neutrinos, ii) the so called $\lambda$ and $\eta$ diagrams. New physics contributions also arise from right-handed currents with right-handed gauge boson $W_R$ mass around $3$~TeV. From the numerical study, we find that the new contributions to $0\nu\beta\beta$ decay not only saturate the current experimental bound but also give lower limit on absolute scale of lightest neutrino mass and favor NH pattern of light neutrino mass hierarchy.